1. Field of the Invention
The present invention relates to an identification information access device that is configured to access a greater number of neighboring game chips which are identical in shape used in, for example, casinos.
2. Description of the Related Art
In casinos, a game chip into which an RFID tag is integrated is used to determine whether the game chip is authentic or to automatically measure the number of the game chips. In particular, an antenna for reading an RFID is provided below a game table and the antenna generates a magnetic field. The generated magnetic field penetrates the game chips placed on the game table to produce electromotive force in the RFID tag and detects identification information (unique ID) of bet chips (for example, refer to United States Patent Publication No. 2003/0092491 and Japanese Patent No. 4409540).
In a case in which plural antennas are provided for the reading and writing, processing to select one of these antennas is necessary (for example, refer to United States Patent Publication No. 2009/0093293).
In the devices described in United States Patent Publication No. 2003/0092491 and Japanese Patent No. 4409540, a range of the magnetic field is determined by the shape of the antenna and by the output of RF signals applied to the antenna. If the RFID tag is separated from the antenna by a predetermined distance in accordance with sensitivity of the RFID tag, electromotive force necessary to operate the IC is not produced in the RFID tag. Therefore, reading information, such as identification information of the RFID tag, has been difficult.
In some situation, for example, plural game chips are stacked on a game table. At positions near the game table, the distance to the antenna is short and thus intensity of the magnetic field is large. Therefore, it is possible to produce sufficient electromotive force and to read the RFID tag. However, at positions separated from the game table, the distance to the antenna is long and thus intensity of the magnetic field is small. Therefore, it is not possible to produce sufficient electromotive force and reading the RFID tag is difficult. There is a case that, when plural game chips are stacked on the game table, reading the RFID tags of all the stacked game chips is difficult. The distance to the position at which the RFID tag can be read is typically determined by, for example, intensity of the electromagnetic wave and sensitivity of the RFID tag: therefore, the distance is not uniformly determined.
In the device described in United States Patent Publication No. 2009/0093293, it is necessary to perform processing to select one of plural antennas. It takes time to complete reading from and writing in all of the plural antennas. In addition to that, the processing to select antennas makes control processing be complicated. Further, there is a possibility that interference occurs between the plural antennas, and check processing is necessary after the reading and writing. This takes time and makes the processing be complicated.
The present invention has been made in view of circumstance described above, and an object thereof is to provide an identification information access device that is configured to read identification information stored in an RFID tag even if the RFID tag is located at a position at which it has been considered to be difficult to read the RFID tag because of the long distance from an antenna.